From June to August, everywhere in Japan soba or somen noodles are eaten cold. So pervasive is the custom, the dish is simply called Summer Noodles. At the Japanese table, the noodles, condiments, and flavoring sauces are served separately so that each person may dollop and mix according to personal preference. The basic set of three condiments — ginger, scallion, and wasabi — are pretty much de rigeuer. A more expansive presentation might include a plate of thinly sliced shiitakes simmered in a seasoned dashi, finely shredded Japanese egg omelet, finely shredded roasted nori, and grated daikon or carrot.

Whisk together the wasabi powder and 1-1/2 tablespoons water in a small bowl. Set aside for 5 minutes.

Stir the soy sauce into the dashi and set on the table. Set out separate dishes containing the wasabi paste, ginger, and scallions. Divide the noodles among four bowls and serve, surrounded by the condiments already on the table.